move blinding_privkey from onion_message to lnonion

electrum/lnonion.py

@@ -193,6 +193,17 @@ def get_blinded_node_id(node_id: bytes, shared_secret: bytes):
     return blinded_node_id.get_public_key_bytes()
 
 
+def blinding_privkey(privkey: bytes, blinding: bytes) -> bytes:
+    shared_secret = get_ecdh(privkey, blinding)
+    b_hmac = get_bolt04_onion_key(b'blinded_node_id', shared_secret)
+    b_hmac_int = int.from_bytes(b_hmac, byteorder="big")
+
+    our_privkey_int = int.from_bytes(privkey, byteorder="big")
+    our_privkey_int = our_privkey_int * b_hmac_int % ecc.CURVE_ORDER
+    our_privkey = our_privkey_int.to_bytes(32, byteorder="big")
+    return our_privkey
+
+
 def new_onion_packet(
     payment_path_pubkeys: Sequence[bytes],
     session_key: bytes,

electrum/onion_message.py

@@ -40,7 +40,7 @@ from electrum.lnrouter import PathEdge
 from electrum.logging import get_logger, Logger
 from electrum.crypto import sha256, get_ecdh
 from electrum.lnmsg import OnionWireSerializer
-from electrum.lnonion import (get_bolt04_onion_key, OnionPacket, process_onion_packet,
+from electrum.lnonion import (get_bolt04_onion_key, OnionPacket, process_onion_packet, blinding_privkey,
                               OnionHopsDataSingle, decrypt_onionmsg_data_tlv, encrypt_onionmsg_data_tlv,
                               get_shared_secrets_along_route, new_onion_packet, encrypt_hops_recipient_data)
 from electrum.lnutil import LnFeatures, MIN_FINAL_CLTV_DELTA_ACCEPTED, MAXIMUM_REMOTE_TO_SELF_DELAY_ACCEPTED
@@ -145,18 +145,6 @@ def encode_blinded_path(blinded_path: dict):
         return blinded_path_fd.getvalue()
 
 
-def blinding_privkey(privkey: bytes, blinding: bytes) -> bytes:
-    shared_secret = get_ecdh(privkey, blinding)
-    b_hmac = get_bolt04_onion_key(b'blinded_node_id', shared_secret)
-    b_hmac_int = int.from_bytes(b_hmac, byteorder="big")
-
-    our_privkey_int = int.from_bytes(privkey, byteorder="big")
-    our_privkey_int = our_privkey_int * b_hmac_int % ecc.CURVE_ORDER
-    our_privkey = our_privkey_int.to_bytes(32, byteorder="big")
-
-    return our_privkey
-
-
 def is_onion_message_node(node_id: bytes, node_info: Optional['NodeInfo']) -> bool:
     if not node_info:
         return False

tests/test_onion_message.py

@@ -17,12 +17,12 @@ from electrum.lnmsg import decode_msg, OnionWireSerializer
 from electrum.lnonion import (
     OnionHopsDataSingle, OnionPacket, process_onion_packet, get_bolt04_onion_key, encrypt_onionmsg_data_tlv,
     get_shared_secrets_along_route, new_onion_packet, ONION_MESSAGE_LARGE_SIZE, HOPS_DATA_SIZE, InvalidPayloadSize,
-    encrypt_hops_recipient_data)
+    encrypt_hops_recipient_data, blinding_privkey)
 from electrum.crypto import get_ecdh, privkey_to_pubkey
 from electrum.lntransport import LNPeerAddr
 from electrum.lnutil import LnFeatures, Keypair, MIN_FINAL_CLTV_DELTA_ACCEPTED, REMOTE
 from electrum.onion_message import (
-    blinding_privkey, create_blinded_path,OnionMessageManager, NoRouteFound, Timeout, get_blinded_paths_to_me,
+    create_blinded_path, OnionMessageManager, NoRouteFound, Timeout, get_blinded_paths_to_me,
 )
 from electrum.util import bfh, read_json_file, OldTaskGroup, get_asyncio_loop
 from electrum.logging import console_stderr_handler